Adaptive immunity

Question 1

List the 6 cellular components and the humoral component of the adaptive immune system.

Answer 1

B-lymphocytes including plasma cells

Cytotoxic T- lymphocytes

Helper T- lymphocytes

Regulatory T- lymphocytes

Antigen-presenting cells

Memory cells

Antibodies (immunoglobulins, Ig – various classes)

Question 2

Where do T cells mature?

Answer 2

Thymus gland

Question 3

What is the function of B cells?

Answer 3

Produce antibodies (immunoglobulins)

Question 4

What is the function of helper T cells?

Answer 4

Secrete cytokines that activate other immune cells

Question 5

What is the function of cytotoxic T cells?

Answer 5

Directly kill infected cells and tumour cells

Question 6

What happens when the an antigen binds to the antigen-receptor (surface immunoglobulin) on the surface of a B cell?

Answer 6

The B cell becomes activated and differentiates into a plasma cell, which are specialized in producing and secreting the same antibody at a high rate

Question 7

How does the size of the nucleus and endoplasmic reticulum change as B cells differentiate into plasma cells and why?

Answer 7

The nucleus becomes smaller as a result of the increased size of the endoplasmic reticulum, because the endoplasmic reticulum is involved in the secretion of the soluble form of the immunoglobulin

Question 8

Describe 3 ways in which antibody binding to an antigen can aid in the removal / destruction of pathogens.

Answer 8

Block a pathogen from causing harm

Mark a pathogen for phagocytosis (opsonisation)

Activate the complement system

Question 9

Which feature of antigens means that different antibodies can bind to separate parts of the same antigen?

Answer 9

Epitopes

Question 10

What is clonal selection in the adaptive immune response?

Answer 10

The activation and proliferation of a specific lymphocyte that produces the antibodies which bind the same antigen

Question 11

Which cells are usually needed for the activation of B cells?

Answer 11

Helper T cells

Question 12

Describe why a secondary antibody response to an antigen would be quicker and stronger than the primary antibody response.

Answer 12

Due to immunological memory – the first exposure produces clonal expansion to produce plasma cells and memory B cells. Upon subsequent exposure, the memory B cells recognise the antigen much more quickly

Question 13

What is the typical antibody class switch in an immune response?

Answer 13

IgM to IgG

Question 14

What is the cell surface protein of cytotoxic T cells?

Answer 14

CD8

Question 15

What is the cell surface protein of helper T cells?

Answer 15

CD4

Question 16

What is the function of TH1 cells and what do they activate?

Answer 16

Secrete cytokines (interferon-y) that mainly activate virally infected cells, macrophages, and other T cells

Question 17

What is the function of TH2 cells and what do they activate?

Answer 17

Secrete cytokines (interleukins) that mainly activate B cells

Question 18

Describe the structure of the T cell receptor and how this relates to antigen recognition.

Answer 18

TCRs are alpha beta heterodimers, with both the alpha chain and the beta chain having a constant and variable region each

The variable regions are where the antigen recognition occurs, as they form the binding site for the peptide-MHCs (i.e. antigen)

Question 19

What are the MHC proteins, where are they present, and what are they recognised by?

Answer 19

MHC Class I – present on most cells, recognised by CD8+ cytotoxic T cells

MHC Class II – present on antigen-presenting cells, recognised by CD4+ helper T cells

Question 20

Describe the structure of MHC Class I proteins.

Answer 20

Composed of an alpha chain and b2-microglobulin

The alpha chain forms the antigen-binding groove

Question 21

Where are the peptides presented on MHC Class I proteins derived from?

Answer 21

Cell cytoplasm

Question 22

Describe the structure of MHC Class II proteins.

Answer 22

Composed of alpha and beta chain which form the antigen-binding groove where peptides are displayed

Question 23

Where are the peptides presented on MHC Class II proteins derived from?

Answer 23

Ingested material

Question 24

Do CD4 and CD8 bind to the variable or non-variable parts of the MHC proteins?

Answer 24

Non-variable